Outside Temperatures and Sun Exposure May Trigger Glaucoma

Outside Temperatures and Sun Exposure May Trigger Glaucoma

Study published in August issue of Archives of Ophthalmology

BOSTON (Aug. 9, 2011) -- Exfoliation syndrome, also known as pseudoexfoliation syndrome, is an eye condition that produces considerable ocular burden. In addition to being the leading cause of secondary open angle glaucoma, exfoliation syndrome (ES) is associated with increased risk of cataract as well as cataract surgery complications.

“A prior report that common genetic variants in the lysyl oxidase-like 1 gene (LOXL1) are associated with ES represented a landmark discovery in our understanding of this condition,” said Louis Pasquale, M.D., co-author and director of the Massachusetts Eye and Ear Infirmary’s Glaucoma Center of Excellence. “Interestingly, while point prevalence estimates of ES vary from ~0 to 20% around the globe, the portion of people with disease-associated LOXL1 variants is remarkably constant. This prompted our group to search for environmental factors associated with ES.”

Researchers from the Mass. Eye and Ear, Harvard Medical School, Boston, Mass.; Department of Ophthalmology and Visual Sciences, Kellogg Eye Center, University of Michigan, Ann Arbor, Mich.; Department of Medicine, Channing Laboratory, Brigham and Women's Hospital, Boston, Mass., and Departments of Biostatistics and Epidemiology, University of Michigan School of Public Health, Ann Arbor, set out to find out if geographic and climatic risk factors are associated with ES. Their study is published in the August issue of the journal Archives of Ophthalmology.

The researchers performed a retrospective study of 626,901 eye care recipients, dating from 2001 to 2007 from 47 US states in a managed care network. Incident ES cases-patients (N = 3367) were identified by using billing codes. The scientists assessed the risk of ES by geographic latitude tier in the continental United States and assigned state-level climatic data (erg, ambient temperature, elevation, and sun exposure) according to patients' residential location. The hazard of ES was calculated by using multivariable-adjusted Cox proportional hazards regression models.

“This large prospective cohort study demonstrates that there is a positive association between latitude and ES risk that is robust and not related to demographic features or other systemic covariates,” Dr. Pasquale explained. “Climatic analyses indicate that lower ambient temperature interacts with increased solar exposure to increase the risk of ES. This is the first work to demonstrate a relation between increasing latitude and a condition with a strong predisposition to glaucoma. State-by-state analysis revealed that relative to most recent residence in Missouri, living in Maine was associated with a 5-fold increased risk of Exfoliation Syndrome in multivariable analysis. More work is needed to determine how these environmental factors conspire to contribute to ES.”

According to the National Eye Institute, ES is the major known cause of primary open-angle glaucoma, which affects more than 2 million individuals in the United States and is one of the leading causes of blindness. With the rapid aging of the U.S. population, the number of individuals affected by the disease will increase to more than 3 million by 2020.

The Massachusetts Eye and Ear Infirmary is an international center for treatment and research and a teaching hospital of Harvard Medical School. For more information, call (617) 523-7900 or TDD (617) 523-5498 or visit www.MassEyeAndEar.org